Name: Craig. R. Eckberg

Title: Manager, Air Resources Company: NRG Texas Power LLC Sign Date: 6/30/2010 Name: MarkRoach, P.E. Title: Techical Leader, Source Groups Company:Clean air Engineering Sign Date: 6/30/2010 Permitted Facility Representative / Date Testing Company Representative / Date



### Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station Final Test Report for

/ / Based on information and belief formed after reasonable inquiry, I certify that the statements and information in this test report are true, accurate, and complete. I have reviewed all testing details and results in this test report and hereby certify that the test report is authentic and accurate.

Wednesday, February 23, 2011 Page 1 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 Facility Information: Limestone 9 miles north of Jewett TX on FM 39

Jewett TX75846 Contact:Craig R. Eckberg Phone:713-795-6208 Fax: 713-795-7431 Email: craig.eckberg@nrgenergy.com Testing Company: Clean Air Engineering, Inc. 321 Century Plaza Drive Suite 130 Houston TX77073 Contact:Bart DeLatte Phone:281-443-6400 Fax: 281-443-1806 Email:bdelatte@cleanair.com

Air Permit Number: O75 Permitted Source ID/Name: LIM1 Unit 1 Permitted Maximum Process Rate: N/A Max. Normal Operation Process Rate: N/A Target Process Test Rate N/A

Description of the source (including control equipment). Please see the attachments for source or process flow diagram: This description should describe the process and associated controls to differentiate this facility from, or document similarity with others of same SCC.

The following describes any modifications and/or deviations to the applicable test methods. If alternative methods were requested, see the attachments for documentation of request AND approval, including dates. Industry/SCC/NAIS221112

Sampling Location Information:

Test Parameter Information: AFS #:4828900010 FRS #:110034223668

SCC / Description10100202 External Combustion Boilers - Electric Generation - Bituminous/Subbituminous Coal - Pulverized Coal: Dry Bottom (Bituminous Coal)
The following state and federal regulations that apply to the proposed testing:

Location Round

Duct Diam. Distance from upstream dist. Distance from

downstream dist. Number of

Traverse Ports Equiv. Diam Min.Travers Points Rect. Duct Length /Width Stack Exit 357 960 4620 4 0 12 0 0

Target Parameter Test Method Number of

Test Runs Test Run

DurationSample

Points Comments Location% H2O Method 1 - 4 3 120 0 Alt Method 320 Stack Exit Carbon Monoxide Method 10 3 120 0 Alt Method 320 Stack Exit Formaldehyde Method 0011 3 120 0 Alt Method 320 Stack Exit Total organic compounds

(TOC) as Propane Method 25A 3 120 0 Stack Exit
Co2 Method 3A CO2 3 120 0 Stack Exit O2 Method 3A O2 3 120 0 Stack Exit
Wednesday, February 23, 2011 Page 2 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 The following describes any modifications and/or deviations to the applicable test methods. If alternative methods were requested, see the attachments for documentation of request AND approval, including dates. The following compounds will be determined by US EPA Mehtod 320: Formaldehyde, CO, Methane, Moisture. Described in protocol.

Wednesday, February 23, 2011 Page 3 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 Sampling / Stack Data Results Summary LocationStack Exit - Method 25A Average Run Number 1 2 3 Test Date 4/20/2010 4/20/2010 4/20/2010 Run Start Time 9:50:00 AM1:02:00 PM 3:47:00 PM Run Finish Time 12:05:00 PM3:23:00 PM 6:02:00 PM Carbon Dioxide, % 14.55 14.56 14.47 14.527 Oxygen, % 5.02 5.11 5.12 5.083 Dry Volumetric Flow Rate, dry scfm 1760000 1746000 17610001,755,666.66 7 F-Factor, dscfm/MMBtu @ %O2 10209 10224 10179 10,204.000 Moisture, % 18.55 18.47 18.64 18.553 Fuel Type Override Override Override Fw 11875 11875 11845 11,865.000 Fc 1910 1910 1910 1,910.000

Wednesday, February 23, 2011 Page 4 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 Emissions Summary

Process Run Data Location: Stack Exit - Method 25A Compound: Total organic compounds (TOC) as Average Run 1 2 3 lb/mmBtuO2 1.05E-04 0.00E+00 0.00E+00 0.000 ppm 6.81E-02 0.00E+00 0.00E+00 0.023 ppm@7%O2 5.96E-02 0.00E+00 0.00E+00 0.020

Wednesday, February 23, 2011 Page 5 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 Process Run Data

Run Name Value UOM Comments Target Value 1 Coal Firing Rate 584.51 TPH 590 2 Coal Firing Rate 565.56 TPH 590 3 Coal Firing Rate 570.12 TPH 590 1 Average Heat Input 8645 MMBtu/hr 7870 2 Average Heat Input 8629 MMBtu/hr 7870 3 Average Heat Input 8737 MMBtu/hr 7870 1 Steam Output 61141000 lb steam/hr6100 2 Steam Output 60981000 lb steam/hr6100 3 Steam Output 61241000 lb steam/hr6100 1 Synfuel Firing Rate 0 0 2 Synfuel Firing Rate 0 0 3 Synfuel Firing Rate 0 0 1 Petroleum Coke Firing Rate 0 0 2 Petroleum Coke Firing Rate 0 0 3 Petroleum Coke Firing Rate 0 0 1 Coal Gas Firing Rate 0 0 2 Coal Gas Firing Rate 0 0 3 Coal Gas Firing Rate 0 0 1 Fuel Oil Firing Rate 0 0 2 Fuel Oil Firing Rate 0 0 3 Fuel Oil Firing Rate 0 0 1 Flue Gas Flow Rate 2E+06 dscfm 2E+06 1 Pressure Drop Across FGD (if applicable) 0 in H20 0 1 FGD Scrubber Liquor pH 0 pH 0 1 FGD Scrubber Liquor Flow Rate 0 gal/min 0 1 Sorbent Type and Sorbent Injection Rate (if applicable) 0 lb/hr 0
1 Flue Gas Oxygen Content 5.02 % 5.1 1 Flue Gas Carbon Dioxide Content 14.55 % 14 1 Flue Gas Moisture Content 18.55 % 18 1 Flue Gas Sampling Point Temperature 158 Deg F 160 1 Flue Gas Pressure 0 atm 0 1 Standard Pressure 1 atm 1 1 Standard Temperature 68 Deg F 68 Wednesday, February 23, 2011 Page 6 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010

APCD Run Data

Process Lab Run Data 1 Unit Gross Electrical Output 887 MW 890 1 Unit Net Electric Generation 1897 MWh 1900

Run Name Value UOM Comments Target Value 1 LOW NOX BURNERS 0 0 1 OVERFIRE AIR 0 0 1 SPRAY SCRUBBER 0 0 1 ELECTROSTATIC PRECIPITATOR 0 0

Run Name ValueUOM Comments 1 Fuel Higher Heating Value 10312Btu/lb 2 Fuel Higher Heating Value 10335Btu/lb 3 Fuel Higher Heating Value 10788Btu/lb 1 Fuel Moisture 31.19 % 2 Fuel Moisture 30.87 % 3 Fuel Moisture 31.46 % 1 Moisture as determined 13.4 % 2 Moisture as determined 15.1 % 3 Moisture as determined 14.9 % 1 Volatile Matter 41.8 % 2 Volatile Matter 41.04 % 3 Volatile Matter 42.76 % 1 Ash 18.03 % 2 Ash 15.95 % 3 Ash 14.86 % 1 Fixed Carbon 40.17 % 2 Fixed Carbon 43.01 % 3 Fixed Carbon 42.38 % 1 Carbon 62.77 % 2 Carbon 63.29 % 3 Carbon 65.26 % 1 Hydrogen 3.97 % 2 Hydrogen 3.98 % 3 Hydrogen 4.32 % 1 Nitrogen 1.07 % 2 Nitrogen 1.04 % 3 Nitrogen 1.14 % 1 Sulfur 1.12 %
Wednesday, February 23, 2011 Page 7 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 2 Sulfur 1.4 % 3 Sulfur 0.69 % 1 Oxygen 13.04 % 2 Oxygen 14.34 % 3 Oxygen 13.73 %

Wednesday, February 23, 2011 Page 8 of 9Utility Boiler MACT ICR Testing Unit 1 Limestone Generating Station 6/30/2010 Sampling / Stack Data Results Detail LocationStack Exit - Method 25A Average Run Number 1 2 3 Test Date 4/20/2010 4/20/2010 4/20/2010 Run Start Time 9:50:00 AM1:02:00 PM 3:47:00 PM Run Finish Time 12:05:00 PM3:23:00 PM 6:02:00 PM Carbon Dioxide, % 14.55 14.56 14.47 14.527 Oxygen, % 5.02 5.11 5.12 5.083 Fuel Factor 1.09 1.08 1.09 Dry Volumetric Flow Rate, dry scfm 1760000 1746000 17610001,755,666.6 67 F-Factor, dscfm/MMBtu @ %O2 10209 10224 1017910,204.000 Moisture, % 18.55 18.47 18.64 18.553 Analyzer Make JUM JUM JUM Analyzer Model 3-300A 3-300A 3-300A Analyzer Serial Number Operating Range 82.98 82.98 82.98 82.980 Operating Units ppm ppm ppm No. Readings/Avg. 60 60 60 60.000 Calibration Set 0 0 0 0.000 Calibration Pre Zero Cylinder ID cc79769 cc79769 cc79769 Calibration Pre Zero Cylinder Instrument Response 0.018 -0.028 0.027 0.006 Calibration Pre Zero Cylinder Bias -0.12 -0.06 -0.11 -0.097 Calibration Pre Zero Cylinder Drift 0 0 0 0.000 Calibration Pre High Cylinder ID alm060394 alm060394 alm060394 Calibration Pre High Cylinder Instrument Response 25.828 25.069 24.939 25.279 Calibration Pre High Cylinder Bias 0.48 -0.91 -0.59 -0.340 Calibration Pre High Cylinder Drift 0 0 0 0.000 Calibration Post Zero Cylinder ID cc79769 cc79769 cc79769 Calibration Post Zero Cylinder Instrument Response -0.028 0.027 -0.111 -0.037 Calibration Post Zero Cylinder Bias -0.18 0.01 -0.28 -0.150 Calibration Post Zero Cylinder Drift 0.06 0.07 0 0.043 Calibration Post High Cylinder ID alm060394 alm060394 alm060394 Calibration Post High Cylinder Instrument Response 25.069 24.939 24.779 24.929 Calibration Post High Cylinder Bias -0.43 -1.07 -0.78 -0.760 Calibration Post High Cylinder Drift 0.91 0.16 0.19 0.420 Cavg 0.051 -0.083 -0.155 -0.062 Cavg Units ppmvw ppmvw ppmvw Cgas 0.0681 0 0 0.023 Cgas Units ppmvd ppmvd ppmvd Fuel Type Override Override Override Fw 11875 11875 1184511,865.000 Fc 1910 1910 19101,910.000 Cgasw 5.5442277093 5235E-02 0 0 0.018 Cgasw Units ppmvw ppmvw ppmvw

Wednesday, February 23, 2011 Page 9 of 9